1. Field of the Invention
This invention relates to sense amplifier circuits and more particularly to a sense amplifier circuit in which there is provided a positive latching feedback to the input of the amplifier to latch on the amplifier input and the gain in the amplifier.
2. Description of the Prior Art
Negative feedback differential amplifiers are well known in the prior art. The IBM Technical Disclosure Bulletin, Vol. 12, #12, May 1970, shows a basic negative feedback differential amplifier. Such an amplifier essentially consists of two current sense shunt feedback amplifiers connected to a differential configuration such that current input signals on the sense line are amplified and fed through the negative feedback transistor to the output. The feedback resistors between the output and the inputs of the amplifier are chosen so that the gain on the feedback amplifier is sufficient to trigger a detector circuit when a signal appears at either input. Variations on this basic differential negative feedback amplifier are also shown in U.S. Pat. No. 3,899,777.
U.S. Pat. No. 3,745,539 also discloses still another latching negative feedback amplifier.
U.S. Pat. No. 4,027,176 teaches a sense circuit in which an output is detected by a differential amplifier controlling a latch with feedback.
U.S. Pat. No. 3,621,301 teaches a special responsive negative latching circuit used in positive feedback.
Generally, in differential sense amplifiers, error signals occur because of structural differences in the individual amplifiers which are coupled together.
Thus structural differences in the differential amplifiers cause an asymmetry which cannnot be avoided so that a differential current independent of the actual current at the input of the read amplifier flows and the output of such amplifier is a function not only of the amplified input signals but the amplified error signals as well. Moreover since such amplifiers are usually used in a cascade arrangement, i.e., the output of a first amplifier is coupled into the inputs of a second amplifier, any error signal is not only amplified within the amplifier itself but is also further amplified in the subsequent amplifiers through which it passes.